San Diego — Bill Cheek has been fiddling around with radio equipment and monitoring the airwaves in one way or another since the 1950s, when, as a kid, he pried open a brand-new transistor receiver, tinkered with the insides, and managed to pull in a signal from a station in faraway Quito, Ecuador.

As Cheek grew up, his fascination with the frequencies grew too. During the 1960s, he moved into VHF and UHF monitoring, and when the first commercial police scanners hit the market in the 1970s, Cheek began listening in on law-enforcement communications. In time, the Mira Mesa man became one of the country's better-known scanner enthusiasts. Since 1991, Cheek has written, edited, and published The World Scanner Report, a monthly newsletter containing "the hottest, rarest, juiciest, inside stuff about VHF-UHF scanner technology, engineering and operation that you ever saw in your life," according to WSR marketing materials.

Cheek is nothing if not passionate about his hobby. "It turns me on," he tells would-be WSR subscribers on his website, "to point a big ear into the heartbeat of government, law enforcement, military, space, business, commerce, and politics: COMMUNICATIONS. You too? If you're serious about radio, you and I are stepping to the beat of the same drummer."

Last month, that passion got Cheek a lot closer to law enforcement than he ever wanted. In late March, federal agents arrested Cheek and his wife Cindy at their Mira Mesa home on a complaint out of the Eastern District of New York charging the couple with conspiring to use interstate commerce "to distribute prohibited electronic communication intercepting devices."

In an e-mail sent to fellow radio enthusiasts this week, Cheek recounted the arrest.

"At about 7:00 a.m. on Wednesday, March 31, 1999, Cindy and I were enjoying our first cup of coffee of the day when there came a loud banging on the door. We supposed it to be an early-morning overnight FedEx or UPS delivery, so I answered the door.

"A badge was shoved in my face with the announcement that there was a warrant for Cindy's and my arrests and for a search of the premises. I stepped back and a dozen (or so) armed agents from the U.S. Secret Service, FBI, Customs, Postal Inspectors, and even a local cop or two charged in.

"I was handcuffed and put on the couch. Cindy groggily wandered into the area wondering what the commotion was all about and was handcuffed.

"[The] next two hours were a typical TV-style search & seizure situation. Then we were hauled off to be fingerprinted and jailed.

"Since the warrant was issued by a judge in [New York], Cindy and I apparently have to be tried there. It doesn't matter that we can't afford to travel to and fro, coast-to-coast; and that we have no peers in New York (I've never set foot in the state of New York....) The fact is...we'll have to go to New York for the indictment hearing and for the trial, should it go that far. That's the bleak side of it; that coupled with the fact that we can't afford ...to hire competent attorneys who are skilled in electronic communications law...."

According to the complaint, the Cheeks sold a team of undercover New York police five kits over the Internet. The kits unscramble the encrypted messages that pass between mainframe computers at police and fire departments and those onboard computers, or mobile data terminals (MDT), you see in the front seats of police cars these days.

The kits, the complaint alleges, "are primarily useful for the purpose of the surreptitious interception of electronic communications, to wit: mobile data terminal information broadcast by law enforcement agencies and emergency service organizations, in violation of Title 18, United States Code, Section 2512 (1) (a)."

The crackdown, radio buffs insist, is a big mistake. "These decoders you can build at home, and you can use them to monitor legal things, like ham radio and weather pictures that are transmitted over the air," says Lindsay Blanton, a Dallas-based scanning authority and a friend of the Cheeks. "That's what a lot of people use these interfaces for. So the interfaces themselves aren't illegal. What Bill might have gotten himself in trouble for is that when he sold this interface, he said, you know, this interface can be used to decode MDT, too. And that may be where he got himself in trouble. But honestly, I think this is overkill."

U.S. law enforcement began moving some of their communications to MDT back in the 1980s, in an effort to put information about surveillance, ongoing investigations, and other sensitive matters out of earshot of eavesdropping criminals. The transmissions still went out across the airwaves, but to anyone listening in on a regular police scanner, they sounded just like a bunch of electronic beeps, whistles, and screeches, the kind of noises a fax machine makes.

For scanner enthusiasts, the move to MDT took a lot of the fun out of the hobby -- and created something of a challenge for them. As the Cheeks say on their website (www.comtronics.net), "The hell of it is, there is getting to be less and less to hear out there on the airwaves, but at the same time there is more and more to decode! Instead of having to give up radio and take up knitting or crocheting there is every reason to dig deeper into radio."

To help their fellow enthusiasts "dig deeper," the Cheeks posted free instructions on their website on how to build a so-called "data decoder interface," a circuit made from parts readily available at Radio Shack, which transformed the MDT tones the scanner picked up into a series of ones and zeroes. When the decoder and scanner were hooked up to a computer loaded with the right software -- software anonymously written but widely available around the Internet -- users' computer screens would begin filling up with the unencrypted text of the intercepted transmissions. Pretty cool.

For radio buffs who didn't want to "roll their own," the Cheeks offered a fully assembled and tested data decoder interface with a 3.5-inch floppy disk containing the software for $48, delivered.

Many radio buffs, including Blanton, insist that every item in the kit was either legal or, in the case of the decoding program, freely available on the Web. What seems to have irked the feds and caused them to haul the Cheeks into court was the instruction sheet the couple included with the kit, which the government alleges, "explicitly advises users about decoding MDT data and states that COMMtronics would 'leave it up to you (the purchaser) to copy your friends and neighbors driver history information as the traffic cop feeds in their personal data.' "

Of course, intercepting data communications like that without authorization is illegal under the Electronic Communications Privacy Act, the 1986 law that also requires government agents to obtain a court order to get access to electronic communications. And in the complaint filed against the Cheeks, the government talks a lot about the "highly sensitive information" that is transmitted by MDT, including details about suspects' criminal histories, victims' medical records, as well as DMV data.

But cops have been known to use MDT technology for other kinds of communications. In 1991, the case against the Los Angeles police officers accused of beating Rodney King got a big boost when it was learned that computer messages sent via MDT by officers involved in the King arrest included racial slurs and frank admissions of excessive force. These included boasts like, "I haven't beaten anyone this bad in a long time," as well as a description of a domestic dispute involving African-Americans that compared the incident to something "right out of Gorillas in the Mist." (The officer who received the message responded: "HaHaHaHa. Let me guess who be the parties.")

"It's interesting," says Blanton. "I think one of the key reasons [the Cheeks were indicted] is because when the cops use the MDTs, they think of it as a secure connection, where they can talk to other officers without anybody else hearing or monitoring. They believe that the public can't listen to them. Now that people can listen to them, they're really getting bent out of shape. It's a real shame. I think they're really overreacting.

"I am worried about it," Blanton continues. "I am worried about the government coming after me because I have all the plans for building those interfaces on my website. There's nothing illegal about that. But I don't have the time or energy to devote to defending myself legally if that comes up. I've thought about just taking down my website. But that's probably exactly what they want."

On their website, the Cheeks warned potential kit buyers that they were "Not responsible/liable for illegal use of this information and/or these products; nor for the consequences thereof. You must determine the lawfulness of these products for your applications and not use them if illegal. Use of this information and/or these products is 100 percent exclusively at your own risk."

The Cheeks appear to have come to the attention of federal authorities in New York after Keith Knipschild, an unemployed electronics enthusiast from Long Island, posted intercepted MDT communications from Nassau County on his website. It's not clear whether Knipschild was a customer of the Cheeks', but his actions were not very smart.

"Posting that stuff on the Internet was a big no-no," says Blanton.

According to a story in Newsday, "Knipschild's website had 93 pages of police transmissions from March 12, which included criminal histories and warrants, motor-vehicle checks, medical information about victims, and witness statements. Nassau police confirmed the information was transmitted by police on that day."

The Cheeks' arrest, Newsday reported, was "a related case."

Neither the Cheeks nor their lawyers, Howard Frank and Lynn Ball, wanted to talk last week about the charges. "I don't think I have any comment," Frank says. "The case is brand new to me, and I just don't know enough yet to make an intelligent comment. It would just be stupid to say something now when I don't know what's going on."

But scanner buffs said the arrest sent a chill through their community -- at least in the United States.

"There were a number of individuals who were running Web pages to help disseminate that software that could decode pagers or MDT," says Blanton. "What's happened is that now that folks have realized that Bill has been arrested for this, everybody got scared and pulled the information. There's still one individual in the U.K., who, of course, is not subject to U.S. laws, who has posted these applications on his Web page. But anyone in the U.S. who goes to his page [www.kmed70.free serve. co.uk/ kmed70/software.htm]and downloads is probably doing something illegal."